Stormwater treatment systems typically remove solids from stormwater flow. These solids represent a major portion of the pollutant load contained in stormwater runoff. Current federal, state and local stormwater treatment guidelines require that all stormwater runoff receive treatment to prevent the conveyance of pollution to downstream receiving water bodies.
In an attempt to quantify the effectiveness of stormwater treatment solutions, the debris collected in devices that treat stormwater is removed during servicing and analyzed. A major factor in determining the effectiveness of a stormwater treatment device is the amount by weight of the debris removed during servicing. Therefore the greater the amount of debris removed from a device by weight increases its effectiveness.
Servicing a stormwater treatment device requires both human, equipment, and financial resources. Being able to service frequently will yield the capture of more debris, and being able to service quickly with a minimum human and investment will reduce the investment of servicing. In addition, because the environment of stormwater treatment systems is dynamic with the potential of flowing water during servicing, servicing quickly can make a major difference as to whether or not a device is serviceable.
Another issue in servicing is the need to accomplish servicing without having to enter the vault of the stormwater treatment system. It is typical to send a person into a stormwater treatment vault with a handheld spray wand to flush debris toward a mobile vacuum system that removes the debris to a truck. Confined space guidelines set by OSHA dictate that when a person enters a confined space, such as a stormwater vault of a stormwater treatment system, the person entering the vault should be certified to do so and that special safety equipment must be present. Not just anyone can do confined space work and the safety routines can be complicated. The confined space issue can be a barrier to accomplishing the servicing of a stormwater treatment system.
It is typical for a vacuum service truck to have a water supply in an onboard tank that is used to flush debris as needed and generally wash things off. However, the supply of water on the vacuum truck is limited and can run out during the servicing of a stormwater treatment system. If the vacuum truck has to leave the service site to restock its water tank, the loss of time can be significant. To abandon the site to restock the water tank would not only take time but would require the treatment system to be closed up and secured out of safety concerns to the public. In addition, water intrusion into the treatment system while the vacuum truck was away would have to be dealt with which would take additional time and resources.
The prior Weiland et al. U.S. Pat. No. 4,024,881, is for an apparatus for removing gelatinous sludge and solids from a settling basin. Steams of liquid directed into contact with the sludge are used to produce a laminar flow of the sludge toward a withdrawal point.
The present stormwater treatment vault is designed to increase the speed of servicing, use less water to do the servicing, and not require a person to enter the stormwater treatment vault to do the servicing. A primary feature that makes this all possible is the liquefaction of the captured debris from a spray system underneath the collected debris in a vault shaped to direct the debris to a collection point to be removed by a vacuum line. A problem with this system is that as the debris accumulates in the settling chamber it can become highly compacted so that the jets of water applied along the floor of the vault chamber undermines the sediment without the majority of sediment collapsing to the floor and thus creates a bridge of compacted debris over the water jets. In the present system vertical cutting water jets act like a knife to cut into the compacted bridge of sediment which then collapses the bridge of compacted debris that has formed in the vault over the floor water jets. Once the compacted debris has collapsed, the water jets along the floor can drive the collapsed debris to a collection point along an angled floor to a position for pickup by a vacuum hose from a vacuum truck.